import java.util.Scanner;

public class text5 {
    public static int fib(int n){
        if(n==1||n==2)
            return 1;
        return fib(n-1)+fib(n-2);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n= sc.nextInt();
        System.out.println(fib(n));
    }
}
